In recent times the value of personal belongings carried by most people in their day to day business has increased significantly. As well as the replacement cost of devices such as mobile phones, music players, there is also the additional cost of losing or having to replace phone numbers, photographs, music, which are held in the portable devices. Most people understand that having one of these devices stolen or misplaced will be a significant inconvenience in addition to the financial cost of buying a replacement. In the case of a laptop computer, smart phone or other device capable of storing personal data, the replacement cost of the device may be insignificant compared to the value of the information saved therein.
In addition to the personal electronic devices, loss of other more fundamental items people carry on their person such as house keys, car keys, wallets, credit cards, passports, can have a significant impact if they are stolen.
One way to protect these personal items is to place them in a secure environment. However on many occasions this is not possible. At the beach, gymnasium, living in a dormitory, or even just leaving a work space for a short time, exposes personal property to theft. Lockers, desk drawers, cupboards etc. provide some protection, but in most cases can be easily forced open or defeated in some other manner. When this happens, there is no alarm event to alert others the theft is occurring, which is why the loss of personal property in these situations is so prevalent.
Recent statistics indicate that of the total university dormitory population of the USA, about 25% will experience one personal theft a year. When extrapolated across the country to include country clubs, sports facilities, factory/office locker rooms, office desks, the level of personal theft is high and increasing. This is especially so for personal electronic devices which are now so wide spread that it is almost impossible to identify a specific unit as one's own once it has been stolen.
There are any number of devices which will detect the occurrence of movement and provide an alarm when they are moved. Most, if not all of these devices rely on the detection of motion in some way or another. They commonly rely on the motion of an attached object to cause a mechanical motion of part of the device which is then detected and an alert provided. Examples are mercury switch relays, moving pin mechanisms and ball race devices where the movement of an object causes a secondary motion within the detection device, which causes an alarm event.
A problem in detecting the motion of an object as the necessary event to cause an alarm condition is that motion in itself is not necessarily a sufficient condition for an alarm event. For example, if an object is accidentally knocked, it will experience motion even though it may not be subject to continual movement which involves the change in the position or location of something. If the movement of an object is to be the cause for an alarm event, then this condition may be accidentally satisfied and result in a false alarm if only the occurrence of motion is recognized.